I think what the OP means is that on average native speakers understand the language intuitively, while most of the non-natives were taught the rules and structure of the language directly.
Being a non-native english speaker I experienced this often. I have never gotten a useful answer for a question about english from English people. It usually was "oh, I just feel which word is right"...
I find the same. My wife is from another country and we find she has more command of my mother language’s rules and whys and viceversa.
For example she had a hard time expressing when does she say “oui” and when does she say “si”; being such a basic word (probably learnt at age 2), she never had to sit and try to infer the rule explicitly. Whereas every french-as-second-language speaker, this is a basic (explicit) rule that has been discussed in class and memorized before being internalized.
And having the rules more explicitly in the head enables hard reasoning over them, which goes beyond intuitiveness in some contexts.
That’s why I separated the treatment of understanding and explaining. I would still argue that a native English speaker has better skills to explain an English word in English - on average.
